Six millennia ago, farmers living in modern-day Mexico made a wise health move: They domesticated the chili pepper.

Researchers at the Smithsonian Institution recently announced the discovery of a 1,000-year-old (and very dried out) stash of more than 100 cultivated chili peppers, indicating that the Zapotec people who once occupied Mexico's Mitla River Valley ate a cuisine very similar to the spicy fare of the region's modern inhabitants.

The kick that fruit added to prehistoric salsas and stews -- and that it perhaps now adds to your favorite spicy dish -- endows those whose mouths can stand it with health benefits, recent research suggests. The fiery chemical that makes peppers hot also seems to combat diabetes and other health problems.

What gives chili peppers their characteristic punch, and makes our faces turn red and sweaty, is a compound called capsaicin. Foraging mammals give capsaicin a wide berth, which usually prevents the plants from being gobbled up. But some people can't seem to get enough of it.

Beyond its flavor-enhancing qualities, capsaicin may hold clues to fighting diseases as varied as diabetes and prostate cancer, recent research indicates. In a study published in 2006 in the American Journal of Clinical Nutrition, for example, Australian researchers found that adding chili peppers to a person's diet reduces the amount of insulin that appears in the blood after eating. High post-meal insulin levels can lead to type 2 diabetes, so the insulin-blunting effect of the peppers may be protective, the researchers concluded.

The study's 36 participants tried two different kinds of diets -- one bland, except for a spicy meal at the end, and one in which each meal contained some chili pepper. Blood tests showed how each volunteer's body responded to the final, spicy meal, and how they responded to a bland meal. In both comparisons, the spicy meal muted the production of insulin. The study also showed that the beneficial effect of chili peppers was greatest in people who were most overweight, suggesting that they might benefit most from adding spice to their diets, says study coauthor Kiran Ahuja, of the University of Tasmania.

The Australian research team also analyzed capsaicin's effects on cholesterol oxidation, which can lead to the formation of dangerous plaque in blood vessels. "We found that after adding chili to the diet, the LDL, or bad cholesterol, actually resisted oxidation for a longer period of time, (delaying) the development of a major risk for cardiovascular disease," Ahuja says. The team reported that finding last year in the British Journal of Nutrition.

In other studies published in the past two years, researchers working in rodents found evidence that capsaicin injections can inhibit the development and progression of type 2 diabetes and can assist in killing prostate cancer cells.

The promising new research doesn't mean that simply eating chili peppers will prevent or cure diabetes and cancer, however. Getting the dose of capsaicin that induced cell death in the recent prostate cancer study would require eating about three habanero peppers, one of the hottest chilies in the world. But it might be possible to get capsaicin's benefits without ingesting impractically large quantities of the chemical at each meal, suggests Roberta Anding, a dietitian at Baylor College of Medicine and a spokesperson for the American Dietetic Association.

"Consider all the fabulous benefits of spinach, broccoli, turmeric, and capsaicin-perhaps these foods have a synergistic effect, so that the combination of eating a variety of plants will contribute to your overall health," Anding says.

The Zapotec people who lived in the caves along the Mitla River may not have been aware of that, but it seems as though they understood it intuitively. The Smithsonian researchers speculate that the caves' inhabitants used fresh peppers to make zesty salsas and used ground, dried peppers to flavor stews and sauces similar to moles -- much as many Mexicans use them today.

Lead researcher Linda Perry suggests that ever since humans began domesticating chilies around 6,000 years ago, they've cultivated increasingly large -- and increasingly spicy -- peppers. In doing so, they created a food that's only now revealing its true medicinal properties.